1. Field of the Invention
The present invention relates to a sheet feeding roller, such as a pick-up roller, a feed roller, a reverse roller or a transport roller, for transporting paper in an electrophotographic apparatus such as a copying machine, a printer or a facsimile machine.
2. Description of the Art
Sheet feeding rollers are generally required to have a high abrasion resistance and to maintain a friction coefficient for a long time. Further, sheet feeding rollers are required to have low hardness for the purpose of ensuring separation of sheets of paper from each other (ensuring a sufficient nip width) and of preventing damages of paper and the like.
Therefore, there has been proposed a sheet feeding roller comprising a hub (shaft) and a single or two-layer elastic layer(s)formed on an outer peripheral surface of the hub. Where the elastic layer has a single-layer structure, the elastic layer comprises an unfoamed cured body of EPDM (ethylene-propylene-diene rubber), urethane rubber or the like. Where the elastic layer has a two-layer structure, an inner layer thereof comprises a foam cured body of urethane rubber or the like and an outer layer thereof comprises an unfoamed cured body of silicone rubber or the like (see, for example, Japanese Patent No. 3571983).
In recent years, the sheet feeding rollers are required to have lower hardness as a copying machine or the like has been highly sophisticated. However, it is apparent that the sheet feeding roller having a single elastic layer has its limitation to decrease its hardness while securing abrasion resistance and sustainability of friction coefficient. On the other hand, since the inner layer of the sheet feeding roller having a two-layer structure as an elastic layer is a foam cured body, lower hardness can be achieved compared with that having a single elastic layer, however, such a sheet feeding roller has an extremely high cost due to complicated production process including foam formation process.
In view of the foregoing, it is an object of the present invention to provide a sheet feeding roller, available at a lower cost, having lower hardness with securing both abrasion resistance and sustainability of friction coefficient.